1. Field of the Invention
The present invention relates to a structural metal member of substantially U-shaped cross section which can be used in a roof truss or in a floor joist.
2. Description of the Prior Art
The majority of residential house framing is accomplished with wood. Most roofing systems enjoy systems with respect to residential housing have in the past been fabricated and constructed of wooden beams and triangulated cross members. Wood is the material of choice because of cost considerations.
With the increased prices in wood, attention has been given to fabricating roof and flooring systems and indeed the entire structure of a residence out of metal structural members. Heretofore metal structural members could not compete with the cost of conventional wooden structures, but that is changing such that metal can now compete cost wise with wood.
Most structural members are cold formed from sheet metal by rolling, folding or pressing a metal strip in order to form the structural member having the desired cross section. In forming metal structural members, concern must be given for the shape of the structural member in cross section such that it can be easily fabricated into the floor joist or roof truss with the associated support members or webs. Metal offers several advantages since it is lighter in weight, stronger, fire resistant and termite resistant. When discussing roof trusses, they may take on various shapes. The most encountered shape is defined by two upper chords adjoined at their adjacent ends and sloping downwardly and outwardly and the upper chords are attached to a lower chord to form an overall triangular truss. These trusses are spaced apart at a predetermined distance in order to form the support for a roof. Similarly, a floor joist can be constructed by use of an upper chord and a lower chord in parallel disposition with bracing members provided therebetween. These bracing members whether found in the groove truss or the floor joist are commonly referred to as webs.
One problem which has developed with respect to the use of metal structural members for roof trusses or floor joists is that typically, the surface to which the outside sheathing or the floor would be secured to the truss or joist would present the contractor with only a single layered surface for penetration of the fastening means. When fastening a wooden sheathing member to a wooden truss, the fastener, most commonly a nail, penetrates not only the sheathing, but into the roof truss itself such that the nail is frictionally engaged along its entire length. Metal trusses and floor joists which have only a single layer adjacent to the sheathing or floor would allow the nail to be frictionally secured through the sheathing or floor material, and only the single layer of the metal truss or floor joist.
Applicant's invention addresses the overall shape of the chord utilized in the floor joist or the roof truss and also the problem associated with the securing means.